Invasive Species Management

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Current Topics

Need Noxious Weed Advice?

We are able to answer calls and questions. Our hours are Mon -Thur 6:30 am - 5 pm.  See our contact information on the right-hand side of this page.

What We Do

Orange hawkweed flowerhead.The Jefferson County Invasive Species Management program provides the public with information and offers solutions for managing invasive species and supports good stewardship of the land.  

We ensure the compliance with Colorado’s noxious weed, forest pest, and agricultural vertebrate pest regulations on private, county, and state lands.  We also provide technical assistance and support to county departments who are responsible for managing county owned lands.

The program coordinates with private, local, state, and federal agencies to achieve regional pest control.

Who We Are

Canada thistle flower.Our staff includes the Invasive Species Management Coordinator and limited summer help.

Weed of the Month

Each month we will feature a noxious weed to help landowners identify weeds they may encounter on their property.

Knotweed

January 2022

Knotweed

Within North America the invasive knotweeds can be found throughout the northern Midwest and coastal regions.  Originally from Asia, knotweed has been planted as ornamentals since the 1800s.  These large plants have since moved into riparian areas and are forming huge thickets.  

The roots are rhizomatous and change the physical structure of creeks and rivers, which can result in severe erosion and collapse.  In areas like the states of Oregon and Washington, this has severely impacted some native fish spawning regions.  The plants can also grow through asphalt and building foundations.   Knotweeds are also known to be invasive and control efforts are undertaken in Europe, England, New Zealand and Australia.

In Colorado, Japanese, Bohemian, and Giant knotweeds are A-List noxious weeds. Giant knotweed is not well known in Colorado.  Previous reports of Giant knotweed may have been misidentified and are probably the hybrid.

Some features you can use to distinguish the different types include plant height, leaf size, leaf hairs, and size of flower clusters. (Knotweed Comparison Chart)

Bohemian knotweed is a hybrid between Japanese and Giant knotweed. The features are in between both parents and can sometimes be confusing.  

Reproduction includes vegetative through stem and rhizome fragments. There is some seed production but it is complicated.  Plants may have perfect or single sex flowers that may or may not be fertile.

Control requires repeated treatments because the extensive roots and rhizomes will resprout.  The roots can be 6 feet deep and the rhizomes 65 feet long.  First reported in Colorado in 1939, the knotweeds are now found in about 10 of our 63 counties.

 

RESOURCES

 EDDMaps - Japanese knotweed        

 Invasive Species Centre – Bohemian knotweed

 Michigan Department of Natural Resources

 Jones, Daniel, Stephen Pike, Malcolm Thomas, and Denis Murphy. 2011. “Object-Based Image Analysis for Detection of Japanese Knotweed s.l. Taxa (Polygonaceae) in Wales (UK).” Remote Sensing 3 (2): 319–42. https://doi.org/10.3390/rs3020319.

 Japanese knotweed – CABI

 Bohemian knotweed – CABI

 Giant knotweed - CABI

Native Grass Profiles

5394336-WEB-Bruce Bosley
1214062-WEB-Dave Powell

Western Wheatgrass

(Pascoplyrum smithii)      

Photos courtesy of bugwood.org

Western wheatgrass is a long-lived perennial grass that likes sunny, dry, sandy sites.  Its elevation range is between 3000 and 9500 feet. 

This cool-season grass grows erect to 30 inches tall and has rhizomes that form sod.  The narrow (about ¼ inch wide) leaf blades are blue-gray to green and are stiff with a mid-rib.

This grass flowers in June-August.  The flowers are arranged in 4- to 6-inch-long heads.

The ligule is fibrous and reduced.  The auricles are purplish and clasp the stem.

The best time to plant is mid-March through mid-April.

Western wheatgrass is used as forage for livestock and wildlife.  Because of its root structure it is used in revegetation projects and as a soil stabilization species.

Lady Bird Johnson Wildflower Center

NRCS  - Plant Profile (pdf)

SEINET - Plant Description

LG_NoxWeed_2020_cover Opens in new window

A Landowner's Guide - Developing a Noxious Weed Management Plan

We developed this guide to assist landowners.  The information provides steps to develop a management plan for properties that have noxious weeds.

Download your copy

yellow_flag_iris Weed Spotter

The Weed Spotter program is a citizen science based effort to detect 6 high priority species on Jeffco Open Space parks.  Learn more at our Citizen Science page.